Welcome XFCE 4.20 to the FreeBSD ports tree!

Announcement: https://xfce.org/about/news/?post=1734220800

This release has experimental Wayland support, but not all components
have been ported, YMMV. From upstream announcement:

Important Notice: Please be aware that the Wayland support in Xfce
4.20 is experimental. It is recommended for advanced users only,
as you may encounter bugs and experience incomplete functionality.
Proceed with caution!

Highlight of this commit:

- Adding new port x11/libxfce4windowing
- Changing some WWW links to XFCE project gitlab
- Cleaned up Makefiles
- Remove unneeded intltool dependencies
- Added WAYLAND option where applicable, enabled by default

Many thanks to Olivier Duchateau <duchateau.olivier@gmail.com> who
provided a set of patches I started work from.

PR:		283345